Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$122.83	4.138%	$127.9127	$127.91	$127.90	$127.90
Purchase #2	$117.52	10.505%	$129.8655	$129.87	$129.85	$129.90
Purchase #3	$171.76	4.360%	$179.2487	$179.25	$179.25	$179.20
Purchase #4	$178.31	8.490%	$193.4485	$193.45	$193.45	$193.40
Purchase #5	$192.65	13.769%	$219.176	$219.18	$219.20	$219.20
Purchase #6	$113.76	8.584%	$123.5252	$123.53	$123.55	$123.50
Purchase #7	$245.90	4.343%	$256.5794	$256.58	$256.60	$256.60
7 purchase totals =	$1,142.73		$1,229.7560	$1,229.77	$1,229.80	$1,229.70